Research On Automotive Aerodynamic Characteristics And Stability In Crosswinds

The automotive aerodynamics characteristics are very important performance ofthe automotive and the automotive stability in the condition of crosswind acts a veryimportant part. When a vehicle is subjected to crosswinds with high speed, thesurrounding flow fields of the body is changing rapidly, it is easy to cause someunexpected conducts such as roll、yaw、flutter and so on, bringing threats to drivingstability, the driving stability and comfort performance will decrease. In addition, thetrend towards lightweight and low drag vehicles will exacerbate the sensitivity tocrosswinds. With these factors concerned, this thesis carries out a research onaerodynamic character of high speed under crosswind effects.This article, based on automotive aerodynamics, uses the way of numericalsimulation methods, and researches the vehicle’s aerodynamic characteristics underthe crosswind; establish the multi-body dynamic model, analysis and evaluation thevehicle driving stability, the research results could be applied as important referencefor the vehicle crosswind stability research.Firstly, by the numerical simulation methods, researches the aerodynamiccharacteristics of the model under the effects of different crosswind velocities. Theresults shows that the aerodynamic force coefficients、aerodynamic forces and thesurrounding flow fields change with the increasing crosswind velocity.Secondly, to the unsteady crosswind, uses the User-Defined Functions, theunsteady external flow field simulations of the car model are carried out under theeffects of the crosswind whose velocity was increasing with time at different rates.For the same vehicle velocity and the crosswind velocity, the results shows that thehigher varying rate of the crosswind velocity, the larger drag and side force,butsmaller lift.Finally, a multi-body vehicle dynamics model exposed to crosswinds isestablished by the ADAMS software. By the crosswind stability theory, the effects ofthe step crosswind gusts are simulated from the aspects of linear driving test. If it isno crosswind, the vehicle has good straight-line driving capability. When under strongcrosswind, the vehicle needs to reduce vehicle velocity to ensure the safe driving ofthe lateral displacement.In conclusion, some inherent rules and relations of high-speed vehicle stability are revealed in this paper, and discussed the effect of high-speed vehicle handling andstability. The results offer important reference data for researching vehicle handlingstability with the crosswind.